Four of them, in fact - silver, gold, platinum, and palladium -, are minted into coins or cast into ingots and traded on commodity markets. All four are assigned the ISO 4217 currency code. Hence, the role of precious metals as investments, on top of their practical use, drives the demand for them. For thousands of years, precious metals have demanded prices that are much higher than those of common industrial metals, such as nickel (about 36 cents per troy ounce) and copper (about 11 cents per troy ounce). mol-1 (third) Ruthenium-palladium and ruthenium-platinum alloys are used in making electrical contacts for wear resistance. As a matter of fact, ruthenium is a very effective hardener for both palladium and platinum. When a small amount of ruthenium is added to titanium, the latter's corrosion resistance is improved significantly. Current collectible gold coins (the 22-carat gold coins), for example, are made of 92% gold, with silver and copper comprising the rest. The coins in circulation in the United States prior to 1933 were made of 90% gold and 10% copper-silver combined. Canada's official gold bullion coin - The Canadian Gold Maple Leaf - is made of 99.999% gold; and so are these four other gold bullion coins: 1. Entering in a Contract For Difference (CFD): Some of the noted financial services firms, especially those in the United Kingdom, provide Contract for Difference (CFD). In this silver investment vehicle, two parties (a "buyer" and a "seller") enter into a contract, in which the seller agrees to pay the buyer the difference between the current value of silver and its value at contract time. The list is presented in order of increasing atomic number. 1. Ruthenium - VIIIb/5; Ru -> Ru2+ + 2 e-; 0.455 V 2. Rhodium - VIIIb/5; Rh -> Rh2+ + 2 e-; 0.600 V 3. Palladium - VIIIb/5; Pd -> Pd2+ + 2 e-; 0.987 V 4. Silver - Ib/5; Ag -> Ag+ + e-; 0.7996 V 5. Osmium - VIIIb/6; Os + 4 H2O -> OsO4 + 8 H+ + 8 e-; 0.838 V 6. 6. Ruthenium - Karl Karlovich Klaus, a Russian chemist and naturalist, is usually credited with the discovery of ruthenium (in 1844). He discovered it from platinum ore samples he obtained from the Ural Mountains in Russia. He named this precious metal after "ruthenia", the Latin word for Klaus's home country Russia.